The present invention relates to an inkjet head employed in printing devices such as an inkjet printer and a facsimile machine.
In general, the inkjet head has a laminated structure including a plurality of thin plates. The plurality of the thin plates includes a nozzle plate through which a plurality of nozzles are formed. In the inkjet head, the plurality of nozzles communicate with pressure chambers, respectively. The inkjet head further has actuator units that operate to apply pressure to each of the pressure chambers.
By the operation of the actuator units, the pressure chamber sucks/ejects ink so that a certain amount of ink is ejected from each nozzle. Each thin plate has openings that constitute an ink flow channels each connecting the nozzle and the pressure chamber.
The plurality of thin plates include a cover plate which is situated on a pressure chamber side of the nozzle plate and which has an opening corresponding to the nozzle. In a manufacturing process of the inkjet head, an adhesive is applied to an adhesive layer between the cover plate and the nozzle plate, so that the cover plate and the nozzle plate are adhered to each other. Typically, to make the adhesive layer thinner, the adhesive having relatively low viscosity is selected and used.
If the amount of the adhesive applied to the adhesive layer between the cover plate and the nozzle plate is less than an appropriate amount, sufficient adhesive force can not be obtained. Further, in such a case, air gaps may be formed in the adhesive layer, and therefore the ink may enter the air gaps. If the ink stays in the air gaps for a relatively long time, the ink in the air gaps may alter its quality, which deteriorates printing quality.
If the amount of the adhesive is too large, a portion of the adhesive applied to the adhesive layer may flow into the nozzle. If such a phenomenon occurs, the portion of the adhesive sets in the nozzle, and thereby ejecting directions of the ink from the nozzles may become nonuniform.
Japanese Patent Provisional Publication No. 2000-33699 discloses an inkjet head configured such that a diameter of an opening of a cover plate, which is adhered to a nozzle plate having a nozzle orifice, is broadened. With this structure, the accuracy of ejecting operation of ink is not deteriorated even if a portion of the adhesive flows into a nozzle during a manufacturing process. The diameter of the opening of the cover plate is determined by considering the amount of the adhesive that flows into the nozzle.